Low idle

[TG Goose]

Had some previous issues, vacuum leaks, leaking injectors. Fixed those problems, car has never run better. Now its time to fix the one last problem, low idle.

When cold, idles 500-600rpm. if you blip the throttle, it comes down to about 300 for a second, but never stalls, goes right back to 500ish.

Once at operation temp, car idles dead on 750.

Keep in mind I have a smoke machine and it does not leak.

If you unplug the ICV, there is no change whatsoever.
I have another ICV, it actually makes the car idle even lower when warm, about 650, but still cold idles at 500.

Things I have replaced and or tested in the last week:
CTS, O2, Hose clamps, vacuum lines, FPR, Fuel Relay, 02 relay, main relay
Fuel Injectors, TB Gasket, VC Gasket

previous issues outlined in this thread:

http://www.r3vlimited.com/board/showthread.php?t=276574

[oldmann]

Have you tried manually setting the Idle speed with the throttle body. There is a setting for the plate opening when closed.

[jlevie]

Check the idle switch in the TPS (electrically) If that switch is bad or misadjusted, the DME won't know the engines is at idle and thus won't control the ICV.

[TG Goose]

yeah i was thinking it might be the TPS, i have a new one i can try and make sure its adjusted properly

[Slicktop_serg]

I have the same issue but is it really a big problem? Car runs perfectly fine.:-)

[Earendil]

Check the idle switch in the TPS (electrically) If that switch is bad or misadjusted, the DME won't know the engines is at idle and thus won't control the ICV.

Check this one first. It and the associated wires can be easily tested from the cabin by pulling the ECU plug. Check the Bentley for the pinout, it tells you which pins the TPS open and close are, and what the reading should be.

It can also be done from under the hood, but I find this method extremely tedious since you can't actually see the pins when you're working.

[TG Goose]

Update time. First of all, NO vacuum leaks.

TPS seemed/tested ok, but was full of oil so decided to swap it regardless. Went to put on new sensor, no way I was going to be able to get it set, previous owner had screwed with the throttle plate screw and it was siezed in its current spot.

Swapped out the throttle body with a spare one i had, luckily I had a brand new matching boot! (Thank goodness for having 1.5 spare motors kicking around.)
New TPS installed to spec. Install new TB, hook up smoke machine, still leak free!

Fired it up, cold idles at about 800-850ish, warm idle 700. Throttle response is 100x better, the old throttle plates were basically always slightly open when supposed to be closed.

Still getting somewhat crap fuel mileage tho (at least compared to my m42 318ti), is 25mpg decent for these motors?

[TG Goose]

Update time. First of all, NO vacuum leaks.

TPS seemed/tested ok, but was full of oil so decided to swap it regardless. Went to put on new sensor, no way I was going to be able to get it set, previous owner had screwed with the throttle plate screw and it was siezed in its current spot.

Swapped out the throttle body with a spare one i had, luckily I had a brand new matching boot! (Thank goodness for having 1.5 spare motors kicking around.)
New TPS installed to spec. Install new TB, hook up smoke machine, still leak free!

Fired it up, cold idles at about 800-850ish, warm idle 700. Throttle response is 100x better, the old throttle plates were basically always slightly open when supposed to be closed.

Still getting somewhat crap fuel mileage tho (at least compared to my m42 318ti), is 25mpg decent for these motors?

[Varinn]

That's quite good man, so in the end it was your TPS that was causing you the problems? Didn't expect that, I should check mine as well once I get the last vacuum leak on my engine sealed up

[TG Goose]

definitely was a TPS problem, it was the last thing I did and it seemed to fix that last nagging cold idle issue.